I can not speak directly about the 2WDs. My understanding with the 4WDs is that the automatic transmission was equipped with the shorter final drive ratio (4.6:1 vs 4.3:1).
Take a look at the sticker inside the driver's door - it should give indication as to the axle type and ratio.
http://www.nissanforums.com/showthread.php?t=20830 shows some ratios. I have no reason to believe they would have changed between the years you mention.
bp